Found a nifty set here:
http://m.ebay.co.uk/itm/Set-of-4-Tailga ... 3141631008
That includes all 4 for less than buying them both separate.
It was a simple job (could have done with an extra hand to hold the boot open when one was removed but managed ok on my head

Just pull off the old ring clip with a flat head screwdriver, apply pressure and off it pops. Then just clip the new one in, no fiddly clips to position just push fit!
Now my door and glass spring open when pulled and stay at maximum height!